1. Field of the Invention
The present invention relates to a friction stir welding tool and a friction stir welding apparatus.
2. Prior Art
As one of welding methods for welding a material to be welded without melting, there is a friction stir welding method. The friction stir welding method is a method wherein a welding tool, made of cylindrical member substantially harder than the material to be welded, is forcibly inserted into the welding portion of the material to be welded while the tool rotates, thereby welding the material by means of frictional heat generated between the welding tool and the material to be welded while the tool rotates and moves. The friction stir welding method softens the material to be welded due to frictional heat generated between the welding tool and the material to be welded and uses the plastic flow phenomenon associated with the rotation of the welding tool; and the method is based on the principle different from the principle on which an arc welding method for melting a material to be welded is based.
With regard to tool material used for the friction stir welding method, well-known materials are those made of PCBN which is a ceramic (for example, see the patent document 1), those made of W-based material including solid solution reinforcing material such as Re (for example, see the patent document 2), and those made of WC-type ultrahard alloy containing Co (see patent document 3).
[Patent document 1] National publication No. of International Patent Application 2003-532543
[Patent document 2] Japanese Patent Application Laid-open No. 2004-358556
[Patent document 3] Japanese Patent Application Laid-open No. 2005-199281